Two of the controlled explosions were carried out early on Tuesday to let firefighters and scuba divers enter parts of the ship that had been inaccessible.

At least three Italian families have said that although their loved ones were listed among those safely evacuated, they had not heard from them.

Coastguard official Marco Brusco said he held a "glimmer of hope" that some of the missing might have survived, but Giglio mayor Sergio Ortelli said earlier that hopes of finding any of them alive were minimal.

Capt Schettino insisted in an interview before his jailing that he stayed with the vessel to the end, but Clarence Mitchell, who is representing Costa Cruises, said: "Mr Foschi confirmed the captain had been approaching the island of Giglio to 'make a salute'.

"The company says this (incident) was caused by an attempt by the captain to show the ship to the port. But there's a criminal investigation going on and we're not going to say anything that's going to compromise that or the captain's case."

The tragedy could also become an environmental crisis as rough seas battering the ship have raised fears fuel might leak into waters that are part of a protected sanctuary for dolphins, porpoises and whales.

The operators of the cruise liner have blamed the captain for sailing close to land to "show the ship to the port".

The chairman of Costa Cruises said the unauthorised deviation from the route had been taken to "make a salute".

Pier Luigi Foschi has apologised for the tragedy which has left dozens of people injured and the 114,000-tonne Costa Concordia lying on its side off Tuscany.

Explaining that the ship was "ultra safe", he said the captain had made an unauthorised and unapproved deviation from the ship's programmed course.

"This route was put in correctly," he said. "The fact that it left from this course is due solely to a manoeuvre by the commander that was unapproved, unauthorised and unknown to Costa."

Foschi added: "Personally and on behalf of the Costa Crociere (Cruises) I want to say we are very sorry for this tragic accident that's happened."

Below, see photos of the cruise liner after it ran aground off the Isola del Giglio.

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View of the Costa Concordia taken on January 14, 2012, after the cruise ship ran aground and keeled over off the Isola del Giglio, last night. Three people died and about 70 were missing Saturday after an Italian cruise ship with more than 4,000 people on board ran aground and keeled over, sparking scenes of panic. AFP PHOTO/FILIPPO MONTEFORTE